The objective of the research program is to determine whether age-related changes occur in the ability of parotid gland cells to synthesize secretory proteins. We have shown previously that the rate of incorporation of labelled amino acids into the glandular proteins and secretory proteins declines with age in rate parotid glands. To determine whether this decline reflects decremental changes in the cellular process of protein synthesis itself, we have initiated studies to examine the stability of messenger RNA (mRNA) during aging. We isolated polyadenylated mRNA from parotid glands of young (2-3 months) and old (27-29 months) rats and compared the translational activity specific for Alpha-amylase, a major secretory protein of the gland, in a cell-free system of protein synthesis. Preliminary results indicate that the level of mRNA specific for Alpha-amylase is reduced significantly in the gland of the older rats as compared with that of the younger counterparts. This comparison was made based on the amount of radioactivity incoporated into the amylase precursor which had been separated by polyacrylamide gel electrophoresis of the translation products, and identified in autoradiographs by comparing with the migration of authentic Alpha-amylase. We would like to examine the level of mRNA specific for Alpha-amylase in several different age groups to determine whether changes occur in the synthesis of secretory proteins with increasing age. Prior to initiating these studies, however, we wish to establish that the rate of cell-free synthesis of the amylase precursor can be determined by radioactivity incorporation analysis following immunoprecipitation of the translation product using parotid mRNA from relatively inexpensive young rats. Thus, specific aims of the proposed study are, following the cell-free translation of parotid mRNA, to precipitate the amylase precursor by antiamylase antibodies and determine the kinetics of radioactivity incorporation into the translation product.